The simple wording reads that the Lord Chamberlain has been "commanded by the Queen" to invite the holder to the marriage at Westminster Abbey at 11 a.m. on April 29. As for the dress code, guests are asked to wear military uniform, a tailcoat or a business suit.

The invitations went out on Wednesday and Thursday. Meanwhile, 600 of the 1,900 guests also have been invited by the Queen to a reception that she is hosting immediately after the ceremony in the Abbey.

Later, around 300 of those 600 guests are invited to a dinner hosted by William's father, Prince Charles, in the evening at Buckingham Palace.

Prince William's office is not releasing the invitations to those events, as they are private.

The couple is expected to stay in London that night, before starting their honeymoon on April 30.